Fix animation track subpath hint inference.

[SaracenOne]

• Closes AnimationPlayer Inspector never displays correct keyframe data for sub-property keyframe tracks (e.g. position:x, scale:y, modulate:a, etc.) #99115
• Supersedes Fix animation track subproperty hints #104867
• Supersedes Fix position:x track return key type hint of Vector3 in AnimationTrackEditor. #106491

Attempts to fix the issue by removing the bezier hack and handling it in a more elegant way based on @YuriSizov's suggestion #102130 (comment)

I think this should be correct now, but another pair of eyes on this would be appreciated.

[YuriSizov]

Hey, thanks for working more on this! To be clear, I was talking specifically about this change (and the one before it that introduced Variant value = p_node->get(p_property);):

• https://github.com/godotengine/godot/pull/97563/files#diff-7ddf85a6b7336ae16d3af69e100c8056caefabb17fd9ceb406fca03f545a1d7b

Which I think is still in effect as of this PR:

godot/editor/animation_track_editor.cpp

Lines 4393 to 4404 in 0b2a84b

	// Get the value from the subpath.
	Variant value = p_node;
	Vector<String> property_path = p_property.split(":");
	for (const String &E : property_path) {
	if (value.get_type() == Variant::OBJECT) {
	Object *obj = value;
	value = obj->get(E);
	} else {
	value = Variant();
	break;
	}
	}

Though I didn't look too deep into the issues and might've misattributed the cause, I still think that piece needs to be changed. If for nothing else but to avoid inventing ad hoc solutions when there is already one in the engine 🙂